In internal combustion engines for motor vehicles, in order to achieve optimum performance, air intake systems are preferred which do not have a fixed air intake volume but permit adaptation to different operating requirements of the engine. Also, noise suppression is important in this regard.
In EP 0 569 714 A1 an air intake system is disclosed which, for purposes of noise suppression, provides in the air intake system an additional cavity through which the air does not flow. Two selectively connectable resonance tubes (interference tubes) are present which at certain rotational speeds of the internal combustion engine perform a damping of the objectionable sound frequencies.
Furthermore, an air intake system for an internal combustion engine is disclosed in German Offenlegungsschrift 40 41 786 in which a controllable shut-off device is present in order to vary the aperture through which the aspirated air flows.
The shut-off means is situated in a transverse passage between two intake passages and is opened or closed by operational commands from an electronic control. The operational commands depend on the speed of rotation of the internal combustion engine and on the temperature of the outside air, which is determined by a temperature sensor.
A disadvantage in the state of the art is that a not inconsiderable part of the air intake and/or suppressor volume is shut off or is not active in the intake of air. Due to the scarcity of the space available in the engine compartment of modern motor vehicles, this is disadvantageous.